我得到空值的日期这里是我的代码。我已经创建了一个字符串格式和日期传递

data=[('anmol','',27000,'21/01/1998'),('anubhav',25,39000,'20/06/1997'),('ravi',25,8900,''),              ('','',70000,''),('','','','')]`
    from pyspark.sql.types import StringType, IntegerType, StructType, StructField
    schema=StructType([StructField('Name', StringType()),
            StructField('Age', StringType()),
            StructField('Income', StringType()),
            StructField('Date', StringType())])
    from pyspark.sql import SparkSession
    spark = SparkSession.builder.appName("Python Spark SQL basic example")\
    .config("spark.some.config.option", "some-value").getOrCreate()
    df1=spark.createDataFrame(data=data, schema=schema)

这里我正在把字符串日期格式转换成日期格式
df3=df1.select（to_date（df1.Date，'yyyy-MM-dd '）.alias（'dt'））